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Core java - Interview Questions and Answers for 'Itech' - 5 question(s) found - Order By Newest

 Q1. Why every object constructor automatically call super() in Object before its own constructors?Core Java
Ans. Derived object carries the body of its class as well as the body of the parent class. Its body ( member elements ) is initialized using its own class constructor whereas the body ( member elements ) carried from the parent class are initialized using super class constructor. So In order to initialize the elements of the parent class before its own elements are even initialized, super is called.

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   Like      Discuss      Correct / Improve     java   oops   constructor   super   inheritance  object oriented programming (oops)  oops concepts   inheritence     Itech      intermediate

Very Frequently asked. Have been asked in HCL Technologies very frequently ( based on 3 feedback ). Among first few questions in many interviews.
  Q2. Differences between abstract class and interface ?Core Java
Ans. Abstract classes can have both abstract methods ( method declarations ) as well as concrete methods ( inherited to the derived classes ) whereas Interfaces can only have abstract methods ( method declarations ).

A class can extend single abstract class whereas it can implement multiple interfaces.

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 Q3. Is it ok to use optional everywhere just to get over nullpointerexception ?Core Java2017-05-23 08:16:28

Ans. Optional is to be used for arguments / atrributes which are indeed optional i.e the request should continue even if they aren't provided. It should not be used for mandatory attributes or arguments as we would like application to shout out ( with error message / exception trace ) to signify a problem.

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   Like      Discuss      Correct / Improve     optional  nullpointerexception  java8  java 8     Itech

 Q4. Write a class and override the equals and hashcode method ?Core Java2017-05-03 15:32:05

 This question was recently asked at 'Vitech Systems'.This question is still unanswered. Can you please provide an answer.

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 Q5. Can we catch errors in Java ? Core Java2017-05-23 08:21:10

Ans. Yes we can

try {
// code
} catch (Error ex) {
// handling code

but we shouldn't ideally do that as errors are mostly JVM based and not application based and there is rarely we can do something about it. Very likely catching and not re throwing would lead to muting their response or trace.

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   Like      Discuss      Correct / Improve     exception handling  error handling  errors     ITech      intermediate

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